CN105044034A - Real-time measurement method for transparent solution concentration change - Google Patents

Abstract

The invention discloses a real-time measurement method for transparent solution concentration change. The method comprises the following steps of carrying out light intensity fitting on a holographic interferogram by using laser beam interference characteristics, carrying out parameter extraction on the light intensity, calculating the light intensity measured at the selected solution measurement position by using extracted parameter to obtain a real-time interference phase difference, and finally calculating the solution concentration variable quantity according to the linear relation of the phase difference and solution refractive index and the linear relation of the solution refractive index and solution concentration. The method disclosed by the invention can realize the real-time measurement of concentration change of a transparent solution, and has the advantages of real time capability, non contact, high sensitivity, high accuracy and the like.

Description

A kind of method for real-time measurement for clear solution concentration change

Technical field

The invention belongs to chemical engineering kinetic test field, particularly relate to a kind of measuring method being applicable to measure clear solution concentration knots modification.

Background technology

Solution concentration is the important parameter characterizing solution properties.The detection of solution concentration change and measurement are the very important problems in the fields such as pharmacy, material, chemistry.Chemical field, when solution inside reacts, the dynamic change of analytical concentration has great significance to illustrating chemical reaction mechanism.Traditional measurement means can only measure the solution concentration under static state usually as densimeter, photometer etc., and when solution concentration dynamic change, is difficult to reach the real time measure.

Digital holographic microscopy can utilize beam interference hologram image to obtain solution position, quantity, phase place and topographical information simultaneously, when solution concentration changes, can carry out Real Time Observation to solution change.But, there is no the method that solution concentration carries out real-time quantitative measurement at present.

Digital hologram measurement Law is a kind of conventional Dynamic Non-Destruction Measurement, is the development of Holographic interferometry art, it have precision high, on measured object (or field) without impact, the feature such as real-time, be almost the most successful application of digital hologram.Holographic interferometry method and general optical interference detection method similar, they have similar precision and sensitivity, and difference is that general optical detection obtains the mode of interference light for mainly containing point wave-front method and divide amplitude.Wave-front method is divided to be the wavefront of light beam is divided into two or more part interfere, as two-slit interference etc. again: during divide amplitude, the amplitude of light beam to be divided into two or more part, as nearly Ke Erxun interferometer etc.And holographic interference is separately then interfered by the not wavefront in the same time of same light beam. the benefit of this method is the systematic error that can reduce device.Holographic interference not only can measure transparent substance, also can measure nontransparent object.And after digital hologram employing CCD replacement holographic dry plate, hologram stores and processes convenient, and much lower than holographic dry plate of the image recording time of CCD, make the interferometry art of digital hologram more more extensive than the application of optical holography, especially in the process of dynamic process, have more the incomparable advantage of optical holography metering art.

In measurement solution concentration, Master's thesis " measures the research of solution concentration change " based on interferometric method in, interferogram is converted into spectrogram through corresponding computer software by Fourier's change, then solves phase differential through inverse Fourier transform.In addition, in another section of Master's thesis (author: Yuan Boyu etc.) of Shandong University, employing be change the method that lens position obtains carrier fringe to resolve phase differential, the method is easy to destroy light path, increases experiment difficulty and uncertainty.

Summary of the invention

For promoting accuracy of measurement, make up the deficiency that conventional measurement techniques is measured concentration dynamic change solution, the invention provides a kind of method for real-time measurement for clear solution concentration change, thus can be used for that solution concentration in all kinds of metal anode corrosion such as aldary quantitative measurment, crystalline material preparation controls, solution component change detection etc. in catalyst surface concentration change, chemistry and Bioexperiment in solution.

Concrete technical scheme of the present invention is as follows:

For a method for real-time measurement for clear solution concentration change, comprise step:

1) measuring laser is divided into parallel object light and reference light by beam splitter, through clear solution to be measured and the object light carrying solution information collect through imaging len and interfere at beam splitter prism place with reference light, the interference image of formation concentric circles striped;

2) when solution concentration changes, repeat step 1) in operation, obtain occur striped distortion interference image;

3) to step 1) and step 2) in interference image carry out light intensity matching, extract the intensity signal of measurement point in two width figure, calculate to obtain the interference phase difference of measurement point;

4) according to phase differential and the linear relationship of solution refractive index and the linear relationship of solution refractive index and solution concentration, the solution concentration variable quantity of computation and measurement point.

Wherein, described clear solution is contained in transparent sample ware, and is placed between one times of focal length of described imaging len and two times of focal lengths, plays and amplifies micro-effect.

Object light after beam splitting and the light path of reference light are provided with spatial filter filtering and collimation lens, play filter action.

Step 3 described) in, clear solution uniform concentration distribution to be measured, light intensity is expressed as:

$I(x,y)=U_O^2+U_R^2+{2U}_O{U}_R\cos (2\mathrm{\π}{(d^2+R^2)}^{1/2}/\mathrm{\λ})$

In formula, x, y are the coordinate of arbitrfary point, U _ofor the complex amplitude of object light, U _rfor the complex amplitude of reference light, λ is wavelength, d be gather image CCD to the distance between solution, R is the distance of CCD plane any point to the interference image center of circle.

Wherein, interference phase difference be expressed as:

In formula, n _{(x, y)}for the solution refractive index of any point in concentration change process, n ₀for the solution refractive index before concentration change, λ is optical maser wavelength, and d is the width of transparent sample ware.

Described step 4) in, solution refractive index change delta n _{(x, y)}change with phase differential pass is:

In formula, n _{(x, y)}for the solution refractive index of any point in concentration change process, n ₀for the solution refractive index before concentration change, λ is optical maser wavelength, and d is the width of transparent sample ware.

Described step 4) in, solution variations in refractive index and solution concentration change and meet linear relationship,

$\mathrm{\Δn}=\frac{\mathrm{dn}}{\mathrm{dc}}\mathrm{\Δc}$

In formula, it is the coefficient of relationship of concentration change and variations in refractive index.

Step 4 described) in, the computing formula of solution concentration variable quantity is:

In formula, Δ c is solution concentration variable quantity, it is the coefficient of relationship of concentration change and variations in refractive index.

Beneficial effect of the present invention:

(1) Import computer technology and image processing techniques, makes record and analyzes fully digitalization, greatly improving the accuracy and runtime of data processing;

(2) in measuring process, to the solution in sample without any contact, light beam, through after sample cell, is real-time to concentration change reaction in solution, therefore has noncontact and real-time advantage.

Accompanying drawing explanation

Fig. 1 is the index path of measuring system;

In Fig. 2, (a), (b) and (c) are for collecting three width interference images in concentration change process;

The light intensity curve of diverse location and matched curve figure when Fig. 3 is initial;

Fig. 4 is the light intensity curve of diverse location after concentration changes and matched curve figure, and the some position chosen is the position of solution concentration to be measured;

Fig. 5 is the light intensity curve of diverse location after concentration changes and matched curve figure, and the some position chosen is in matched curve, and this brightness present position, in order to calculate phase differential.

Embodiment

Measuring system as shown in Figure 1, comprises laser instrument 1, beam splitter 2, spatial filter 3, lens 4, sample cell 5, lens 6, completely reflecting mirror 7, completely reflecting mirror 8, spatial filter 9, lens 10, beam splitter prism 11, CCD12 and computing machine 13.

Sent the laser of certain wavelength by laser instrument 1, be divided into parallel object light and reference light by beam splitter 2, respectively through spatial filter 3 and spatial filter 9 filtering, collimation lens 4 and 10 collimates, and allows beam diameter expand to and mates with sample specification.Sample cell 5 is placed on object light side, before imaging len 6, between one times of focal length and two times of focal lengths of imaging len 6.The object light and the reference light that carry solution information are interfered at beam splitter prism place 11, and produce a series of concentric circles striped, striped is received by CCD12, computing machine 13 record.In course of reaction, solution concentration changes, and forms concentration gradient, change the refractive index of solution, thus the phase place of object light also changes, and striped produces significantly deformity change, as shown in Figure 2.

In the present embodiment, the detailed process wherein obtaining solution concentration variable quantity is as follows: carry out light intensity matching to holographic interference pattern, parameter extraction is carried out to light intensity, and adopt the parameter extracted to calculate to the light intensity measured by the solution measuring position chosen, obtain real-time interference phase difference, finally just can calculate the concentration change amount of solution according to phase differential and the linear relationship of solution refractive index and the linear relationship of solution refractive index and solution concentration.Wherein detected solution is be contained in the clear solution in transparent sample ware.

Before reaction occurs, solution regards as homogeneous body, and light intensity is expressed as

$I(x,y)=U_O^2+U_R^2+{2U}_O{U}_R\cos (2\mathrm{\π}{(d^2+R^2)}^{1/2}/\mathrm{\λ})---\left(1\right)$

U in formula _ofor the complex amplitude of object light, U _rfor the complex amplitude of reference light, λ is wavelength, and d is the distance near CCD to electrode surface between solution, and interference image shows as a series of concentrically ringed light and shade striped, and R is the distance of CCD plane any point to the center of circle.In Fig. 3, empirical curve is with the interferogram center of circle for initial point is to the brightness I of each point on one ray of electrode side level, and horizontal ordinate is distance initial point distance.Adopt the matching of Origin software, obtain parameters in formula 1, obtain matched curve.After reaction occurs, striped significantly deformity change, the empirical curve in Fig. 3 is no longer close with matched curve.When in research system, certain any concentration changes, first calculate the brightness of this point, as Fig. 4 cursor position, in matched curve, this luminance point is then in Fig. 5 cursor position.Measure its distance, precision is 10 ^-3more than mm, calculates phase differential further.

With CCD plane for x-y plane, its vertical direction is z-axis, then the phase differential of interference fringe in CCD plane can be expressed as

Wherein n _{(x, y, z)}for the solution refractive index of any point in electrolytic cell in course of reaction, n ₀for the solution refractive index before reaction, the solution refractive index namely under blank assay, λ is optical maser wavelength, i.e. 632.8nm.

Only calculate the concentration change in x-y plane in measurement, cell design is become width relative length or highly shorter specification, then experimental system is approximately two-dimentional refractive index field, i.e. the index distribution n of x-y plane _{(x, y)}.Then formula (2) can be reduced to

Wherein d is cell width.

So solution refractive index change delta n _{(x, y)}change with phase differential pass is

From formula (4), the phase differential direct proportionality before solution variations in refractive index and Object light wave.So by comparing certain moment and the object light phase differential before reacting in reaction, the solution refractive index of inscribing when just can calculate this and the difference of reacting front refractive index.

Because the refractive index major solute concentration of solution changes impact, and linear with it, meet

$\mathrm{\Δn}=\frac{\mathrm{dn}}{\mathrm{dc}}\mathrm{\Δc}---\left(5\right)$

Wherein it is the coefficient of relationship of concentration change and variations in refractive index.Convolution (4), the refractive index that formula (5) and interference fringe phase differential and variable concentrations solute are corresponding in a liquid, finally, calculates concentration knots modification and changes in time,

In formula, Δ c is solution concentration variable quantity, it is the coefficient of relationship of concentration change and variations in refractive index.

Claims (8)

1. for a method for real-time measurement for clear solution concentration change, it is characterized in that, comprise step:

1) measuring laser is divided into parallel object light and reference light by beam splitter, through clear solution to be measured and the object light carrying solution information collect through imaging len and interfere at beam splitter prism place with reference light, the interference image of formation concentric circles striped;

2) when solution concentration changes, repeat step 1) in operation, obtain occur striped distortion interference image;

3) to step 1) and step 2) in interference image carry out light intensity matching, extract the intensity signal of measurement point in two width figure, calculate to obtain the interference phase difference of measurement point;

4) according to phase differential and the linear relationship of solution refractive index and the linear relationship of solution refractive index and solution concentration, the solution concentration variable quantity of computation and measurement point.

2., as claimed in claim 1 for the method for real-time measurement of clear solution concentration change, it is characterized in that, described clear solution is contained in transparent sample ware, and is placed between one times of focal length of described imaging len and two times of focal lengths.

3., as claimed in claim 1 for the method for real-time measurement of clear solution concentration change, it is characterized in that, the object light after beam splitting and the light path of reference light are provided with spatial filter filtering and collimation lens.

4., as claimed in claim 1 for the method for real-time measurement of clear solution concentration change, it is characterized in that, the step 3 described) in, clear solution uniform concentration distribution to be measured, light intensity is expressed as:

$I(x,y)=U_O^2+U_R^2+2U_O{U}_R\cos (2\mathrm{\π}{(d^2+R^2)}^{1/2}/\mathrm{\λ})$

In formula, x, y are the coordinate of arbitrfary point, U _ofor the complex amplitude of object light, U _rfor the complex amplitude of reference light, λ is wavelength, d be gather image CCD to the distance between solution, R is the distance of CCD plane any point to the interference image center of circle.

5. the method for real-time measurement for clear solution concentration change as described in claim 1 or 4, is characterized in that, the step 3 described) in, interference phase difference be expressed as:

In formula, n _{(x, y)}for the solution refractive index of any point in concentration change process, n ₀for the solution refractive index before concentration change, λ is optical maser wavelength, and d is the width of transparent sample ware.

6., as claimed in claim 5 for the method for real-time measurement of clear solution concentration change, it is characterized in that, described step 4) in, solution refractive index change delta n _{(x, y)}change with phase differential pass is:

In formula, n _{(x, y)}for the solution refractive index of any point in concentration change process, n ₀for the solution refractive index before concentration change, λ is optical maser wavelength, and d is the width of transparent sample ware.

7., as claimed in claim 6 for the method for real-time measurement of clear solution concentration change, it is characterized in that, described step 4) in, solution variations in refractive index and solution concentration change and meet linear relationship,

$\mathrm{\Δn}=\frac{\mathrm{dn}}{\mathrm{dc}}\mathrm{\Δc}$

In formula, it is the coefficient of relationship of concentration change and variations in refractive index.

8., as claimed in claim 7 for the method for real-time measurement of clear solution concentration change, it is characterized in that, the step 4 described) in, the computing formula of solution concentration variable quantity is:

In formula, Δ c is solution concentration variable quantity, it is the coefficient of relationship of concentration change and variations in refractive index.